William j



W. J FRYER, Jr.

Arch Girder I Patented Aug. 10, I880.

VIINVENTOR'.

WITNESSES.

N, FEIE RS. FHOTO-UTHOGRAPNE UNTTED STATES PATENT Orricn.

VILLIAM J. FRYER, JR, OF NEW YORK, N. Y.

ARCH-GIRDER.

SPECIFICATION forming part of Letters Patent No. 230,933, dated August10, 1880. I Application filed February 4. 1880.

To all whom it may concern Be it known that I, WILLIAM J. FRYER, Jr.,iron founder, of No. 104 Goerck street, in the city of New York, countyand State of New York, have invented a new and useful Improvement inArch-Girders, of which the following is a specification, reference beinghad to the accompanying drawings, in which Figure 1 is a side elevation.Fig. 2 is a plan looking at the under side of my girder, and Fig. 3 is aerosssection on line X X.

A is the upper web of the arched casting. B B are the lower orsupplementary webs. C is the tension-rod, with turn-buckle c. D D arethe abutments.

Similar letters of reference indicate corresponding parts.

The object of my invention is to give increased security to life andproperty in a building by making a tension-rod girder of such a shape asthat it will be less liable to rupture, and therefore stronger and moresecure, and, in the event of being ruptured, that it will not readilylet down the load above.

A bow-string girder may be regarded as a metallic arch of a slightlycurvilinear form with a tie-rod as a cord extending from the abutmentsat the extremes to receivethe horizontal thrust of the arch. Inmanufacturing, the rod is made alittle shorter than thelength of thecasting, and is expanded by heat, and then placed in position in thecasting and allowed to contract in cooling to the proper tension. Afterthe girder is set up in the buildin g a rowlock brick arch is built overthe line of the iron arch as a precaution in case the girder breaks; butthe girder is always supposed to be made ofsufficient strength to safelysupport the imposed load. From the position in which the brick arch isbuilt hard against the iron, the bricks have no chance to settle andcome down to an independent bearing, and so cannot well aid in carryingthe load while the girder remains intact. In sustaining a load bothcompression and extension are brought into play in the girder. Thestrength of the cast-iron arch lies mainly in its web, the flange beingto prevent buckling and for the purpose of building the wall upon.

1n cast-iron the resistance of compression is to that of extension inthe ratio of six to one,

and being arigid crystalline un malleable substance, it becomes a matterof importance to properly proportion the malleable wroughtiron tie-rod,which has a great degree of extensibility, and comes into action inproportion as the girder is loaded. If the tie-rod be too long it doesnot receive its full proportion of the strain until the casting has sofar deflected or straightened itself out as to receive a severe tensilestrain, which cast-iron is feeble to resist. If, as is more frequentlythe case, the tie-rod is made too short and shrunk in, the casting isthereby cambered up and a severe initial strain is given in addition tothe strain proper induced by the load to produce rupture.

An arch-girder is the cheapest and handiest to carry walls of buildingswhere considerable width of opening is required. They are one favoritemode of architectural construction in this country; but numerousfailures in archgirders both abroad and at home have naturally createdconsiderable apprehension as to their security in the minds of personsfamiliar with the subject. I aim to give these girders better sustainingqualities.

In my improved girder to the usual archshaped casting, which may be insection an upright T or an inverted J I add supplementary webs B B. Thelower edges of these webs are so made that the wrought-iron rod 0 liesin the casting. Now, in case the arch becomes broken, say, in thecenter, from an excessive weight above, the casting, in consequence ofthe supplementary webs, will continue to sustain the load as long as therod holds good. The supplementary webs practically reduce thebearing-points from the end abutments to a span of a considerablylessened distance. The rod of a girder rarely gives way, although it hashappened on account of bad weldin lt is-usual to allow one square inchin crosssection of rod for every ten net tons of load placed upon thegirder. This gives an ample limit of safety, and the rod would fullyperform the duties to be required of it in my girder in the event of mycasting breaking. Aside from this, comparing my casting alone with thecasting of an ordinary arch-girder, mine is of superior strength, forthe reason that the depth of web is greatlyincreased, the

combined webs A and B being really the depth of web for the greater partof the span of the girder.

My rod may be made with square heads and shrunk in in the usual way, orit may have screw-threads and nuts on the ends, and put in place Withoutbeing heated at all. If desired the tie-rod need not extend farther thanto the enlarged parts of the Websthat is, it need not go to the extremeends, although the latter plan is the preferable one; and I prefer touse a turn-buckle, c, in connection with the rods, so that the rod canbe screwed up tojust the right degree of tension. In this case I preferto core out the casting at the abutmeuts, so that the tie-rod will slipthrough a hole or thimble, the square heads of the rods corresponding tothe square openings cored out in the abutments.

One or more rods may be used in my girder, and they may be of round orsquare iron. \Vhere double rods are used an advantage is gained withturn-buckles. Both rods can be brought to alike tension almost animpossibility in the usual method of shrinking in. The rods can betightened up or eased at any time.

My arched casting may be made in two or more pieces, and butted togetherand bolted, and in section the casting may be varied to a number ofwell-known forms; or the arch of my girder may be made of wrought-iron,and the abutment-blocks of cast-iron.

My girder has'great additional strength over an ordinary girder. Thecasting is better able to withstand a eambering strain from a too tightrod. It will the better sustain a load when the rod is too loose than anordinary arch-girder, and altogether makes a strong and safe girder ofthe particular kind known as the bow-string or tension-rod arch-girder.

Having thus described my invention, what I claim is- A bow-string girderhaving an arch, A, made with supplementary webs B B and tie-rod 0,arranged and combined substantially in-the manner and for thepurposeherein shown and described.

WM. J. 'FRYER, JR.

Witnesses:

HENRY RIGHMOND, ARTHUR LAWRENCE.

